Production of acrylonitrile



Patented Feb. 2, 1954 Germany m adis'clie Anilin- *& '=S6da'-'Fabrik 'Aktiengesellschaft, Ludwigshafen (Rhine) v A u H I No. 264272 'Glaims priori ty; applicatipnsG-ermany 1 January 9, 195 t 1 (01. 260-4652) unsaturatedca qzsrli fis 's d, by reason of the readiness Withtvhfch' a niojliia adds ton to t e ac iva e double linkage tre m twit ai ms iaV z tril .b t;ra hq s d g L fifi l to' acryl a ida iu tlierm qla lo n as; it ,is well known-tend to-polymerizeat elevatedtemp at siw 1 p, V

:WeghavefOund;contra yto e ation, that ylonitrilecan be atta ned in 95d li 1 leading mixtures of; acrylic-acid and ammonia in the gas phase at high temperatures, preferably above 200 C.,, over waterrrernoying catalysts, for example: phosphoric acid or iph osph A advantageously are deposited 0n"carri ers.

.The most favorable d'eactior temperature ilies between; 250; and 590 Ca but the rea ctiqn also takes place outside the said temperature-ran Practicallyall theiknown water relnoving catalysts'may be used fas catalysts. if hfi'imfg qs as zfor examplealuminum oxide, thorium; i aluminumxsilioatejalun inum b qrate fsil a gel and m ost advantageously free phosphoric acid; acid *r'eacting phosphates; e. :g.= primary magnesium '01 :calcium phosphate, 5 borip acid; or {phosphates of all kinds, as for example acid and/or neutral alkali, ammoniumgberyllium, aluminum, boron, titanium -fa'nd ,likej pho'sphates, salts of organic bases with-"phosphoric 'acids;and, if desired, mixtures of phosphates and free phosphoric acid."

The 'phos'phor ic "acid and7orvxsalts -;thereof may be used as catalysts either as such or deposited on carriers. Suitable" garrierssre" silica gel, pumice; .colge and the like n nst rrier or *Rasc'hig rings located above the catalyst or is vaporised in a vaporiser connected to the upper end of the tube. Both the acrylic acid and the ammonia gas led into the tube, advantageously in about stoichiometrical proportions, are preferably separate- 5 fllflait eirial actiontemperature before 7 ence =cd, is especially suit rease in the yield of diver jld beldW"2'00"C.

Acrylic acid may bese'tiifi ee from the ammo- ;piun acrylate by means of a strong acid "erase 1: 9 rammol per ho'uF- iiite a ddppe i 'vaptirisemlieated ito 250 C. and is led in the vapor phase by means of a current of nitrogen of 12 litres per hour through a heated tube and enters the reaction tube at about 300 C. Ammonia gas, metered 55 by a valve, is led at the rate of 1 gram-mol per .acid vaporiser When 1730 parts of 90 per cent acrylic acid and hour through an iron coil in which it is heated to 380 C. and is introduced at a point about 10 to 20 centimetres below the level of the catalyst through an iron tube passing through the top of the reaction tube into the mixture of acrylic acid and nitrogen flowing through the catalyst. The catalyst is kept at 380 C. In all there are supplied to the reaction tube during 3 hours 235 grams of 99% acrylic acid, 72 litres of ammonia and 36 litres of nitrogen. The reaction product (287 grams) is cooled to about room temperature and separates into two layers; the upper layer (125 grams) contains acrylonitrile and the lower layer (162 grams) contains ammonium acrylate and a little acrylonitrile and acrylic acid.

By separate distillation, the two layers yield in all 108 grams of pure acrylonitrile, corresponding to a yield of about Example 2 Into a refined steel reaction tube of litres capacity charged with 2.5 litres of phosphoric acidsilica gel catalyst containing 20% of phosphoric acid there are led at 350 C. during 14 hours 1830 grams of acrylic acid, employed in an 80% aqueous solution (with an hourly addition of 1.45 gram-mols of acrylic acid) and 504 litres of ammonia (1.49 mols per hour) and 210 litres of nitrogen (0.64 mol per hour). 1991 grams of crude reaction product are obtained from which by distillation as described in Example 1 615 grams of pure acrylonitrile are obtained, corresponding to a yield of about 58% of the theoretical yield.

Example 3 273 grams of 99% acrylic acid (1.25 mols per hour), 60 litres of ammonia (0.835 mol per hour) and 30 litres of nitrogen are passed over 0.7 litre of phosphoric acid-silica gel catalyst containing 20% of phosphoric acid in a copper reaction tube of 1 litre capacity for 3 hours at 350 C. 265 grams of a crude product are formed from which by distillation 109 grams of pure acrylonitrile are obtained, corresponding to a yield of about 55% with reference to the acrylic acid introduced.

Example 4 One litre of a catalyst of granular silica gel (grain size from 4 to 7 millimetres) which contains 30 per cent of primary magnesium phosphate is charged in an electrically heated re- ..action tube of refined steel fitted with an acrylic and an ammonia preheater.

430 parts of ammonia are carried to reaction in this tube at a temperature of 400 C., with the ammonia being about 15 per cent in excess, 830 parts of acrylonitrile are obtained in the course of 6 hours, which amounts to 72.5 per cent of the calculated yield.

What we claim is:

1. A process for the production of acrylonitrile which comprises leading acrylic acid and ammonia in the gas phase at elevated temperatures above 200 C. over a water-removing catalyst containing phosphoric acid, the acrylic acid and the ammonia being separately preheated at a temperature above 200 C. before bringing them together in contact with said catalyst.

2. A process for the production of acrylonitrile which comprises leading acrylic acid and ammonia in the gas phase at temperatures between 250 and 500 C. over a water-removing catalyst containing phosphoric acid, the acrylic acid and the ammonia being separately preheated at a temperature above 200 C. before bringing them together in contact with said catalyst.

3. A process for the production of acrylonitrile which comprises leading acrylic acid and ammonia in the gas phase at elevated temperatures above 200 C. over a water-removing catalyst containing a phosphate, the acrylic acid and the ammonia being separately preheated at a temperature above 200 C. before bringing them together in contact with said catalyst.

4. A process for the production of acrylonitrile which comprises leading acrylic acid and ammonia in the gas phase at elevated temperatures above 200 C. over a water-removing catalyst containin an acid reacting phosphate, the acrylic acid and the ammonia being separately preheated at a temperature above 200 C. before bringing them together in contact with said catalyst.

5. A process for the production of acrylonitrile which comprises leading acrylic acid and ammonia in the gas phase at elevated temperatures above 200 C. over a water-removing catalyst containing primary magnesium phosphate, the acrylic acid and the ammonia being separately preheated at a temperature abov 200 C. before bringing them together in contact with said catalyst.

6. A process for the production of acrylonitrile which comprises leading acrylic acid and ammonia in the gas phase at a temperature above 200 C. over a water-removing catalyst contain ing a compound selected from the class consisting of phosphoric acid and a phosphate, the acrylic acid and the ammonia being separately preheated at a temperature above 200 C. before bringing them together in contact with the cat alyst.

7. A process as claimed in claim 6 wherein the water-removing catalyst is deposited on a silica gel carrier.

8. A process for the production of acrylonitrile which comprises separately preheating acrylic acid and ammonia to a temperature above 250 C. and separately passing the preheated acrylic acid and ammonia into a catalyst bed and bringing them together within the catalyst bed while maintaining a temperature within the range of 250 C. to 500 C. in the catalyst, said catalyst comprising a water-removing catalyst from the group consisting of phosphoric acid and a phosphate.

WALTER REPPE. NIKOLAUS v. KUTEPOW. OTT-O LEICI-ITLE.

Cosby Sept. 13, 1949 

6. A PROCESS FOR THE PRODUCTION OF ACRYLONITRILE WHICH COMPRISES LEADING ACRYLIC ACID AND AMMONIA IN THE GAS PHASE AT A TEMPERATURE ABOVE 200* C. OVER A WATER-REMOVING CATALYST CONTAINING A COMPOUND SELECTED FROM THE CLASS CONSISTING OF PHOSPHORIC ACID AND A PHOSPHATE, THE ACRYLIC ACID AND AMMONIA BEING SEPARATELY PREHEATED AT A TEMPERATURE ABOVE 200* C. BEFORE BRINGING THEM TOGETHER IN CONTACT WITH THE CATALYST. 